M. Harman and M. Blackman, LCP, NIA, have shown that basal and stimulated levels of luteinizing hormone decline with age in the rat pituitary, and G. Roth, LCMB, NIA, has shown that basal and stimulated levels of prolactin increase in the same system. We have been investigating the mechanisms that produce these age- related hormone changes by analyzing the level of messenger RNA produced by the hormone genes as a function of age. Messenger RNAs from intact pituitary cells and from pituitary cells passaged briefly in tissue culture have been quantitated using hybridization with radioactive cDNAs, and these levels have been compared to the corresponding hormone levels measured by radioimmunoassay. Interestingly, prolactin message does not change with age while luteinizing hormone message does. This indicates that the age- related changes in these hormones are implemented by two different molecular mechanisms, one transcriptional and one translational.